1. Field of Invention:
This invention relates generally to multi-channel transparent jackets whose channels are loadable through respective entry slots with microfilm strips to create a reproducible microfiche master, and more particularly to a jacket of this type in which the lowermost channel is pre-loaded with a dummy strip to stiffen or somewhat thicken this channel and, thereby prevent a partially-loaded jacket from buckling or sliding under when a stack of jackets is stored in a file drawer.
2. Prior Art:
The Engelstein U.S. Pat. No. 3,238,655, entitled "Microfiche Master," discloses a microfiche master composed of a transparent jacket formed by two transparent plastic panels laminated together by ribs which are spaced to define a series of parallel channels or chambers adapted to accommodate microfilm strips. The loaded, multi-chambered jacket functions as a microfiche master from which reference copies may be made. This is effected by contact-printing through the front panel which is quite thin, the back panel being thicker to impart body to the jacket. Such microfiche masters are highly useful in storing and disseminating information.
The Engelstein patent points out that to facilitate contact-printing it is important not only that the top panel of the jacket be thin to minimize the separation between the sensitive film of the contact-printer and the microfilm strip in the jacket so as to obviate a loss of optical definition, but it is also essential to avoid any space between the film strip and the overlying top panel. Since this spacing is determined by the ribs which separate the top panel from the bottom panel of the jacket, the thickness of the ribs is made substantially equal to the thickness of the microfilm strip for which the jacket is intended. Thus, the film strip is snugly received within the chamber.
The Dorman U.S. Pat. No. 3,872,645 discloses a machine for loading microfilm into a microfiche jacket, the machine functioning to section the microfilm into strips and to insert the cut pieces into the channels of the microfiche jacket. By the use of this machine, insertions are made by placing the microfiche jacket on an inclined platform carriage which is shiftable to register successive jacket channels with the leading edge of the incoming film, the film being guided along a trackway terminating adjacent the edge of the platform. In operation, a section of the film constituted by one or more microfilm frames is advanced into a selected channel and the trailing edge of the section is severed. The platform is then indexed to the next chamber position for a new insertion.
To facilitate insertion of film strips, the microfiche jacket is provided with entry slots adjacent the front end of the channels, thereby making it possible to insert the film laterally at an angle to the plane of the jacket rather than in an endwise direction which entails exact co-planar alignment of the film with the jacket.
In the jacket disclosed in the Engelstein patent, preformed plastic or paper ribs are adhesively secured to the top and bottom panels. Hence the spacer ribs act as carriers for an adhesive agent to effect lamination. In the Dorman U.S. Pat. No. 4,452,666, there is disclosed a technique for producing a multi-channel jacket in which the channels are defined by "in situ" plastic ribs which are integral with the top and bottom channels of the jacket and serve to maintain a desired spacing therebetween.
These in situ ribs are formed by extruding a set of molten streams of plastic material in parallel paths, the streams in their molten state being fed between webs of transparent "Mylar" panel material advancing toward combining rolls, whereby the streams are compressively bonded to the webs and are integrated therewith to define ribs whose thickness is precisely determined by the adjustable nip of the combining rolls and whose width depends on the cross-sectional area of the streams, which area is controllable. Thus, the same machine may be used to produce jackets for accommodating microfilm strips in a range of gauges, without having to change the rib supply as in prior machines wherein each rib is preformed by a plastic or paper ribbon drawn from a reel.
When loading a multi-channel transparent jacket of the type heretofore known with strips of microfilm, one normally starts with the uppermost channel. Then the channels therebelow are successively filled to an extent depending on how much documentation is to be carried in a given jacket. Since the resultant microfiche master is updatable at a later time, the lowermost channel is often vacant, for this is always the last to be loaded.
Assuming, for example, a transparent jacket having five channels, each capable of storing a microfilm strip of a length carrying ten frames, the maximum capacity of the jacket is then fifty frames. If this jacket is used for record purposes in a commercial operation, say, to provide a microfiche master for orders placed from time to time by a given account, each of which is microfilmed on a separate frame, then the microfilm jacket, when partially loaded, may have only 20 frames, and the lower channels may remain vacant until such time as subsequent orders are microfilmed and loaded into these channels.
The normal commercial practice is to store the microfiche masters for the various accounts in a file drawer so that when a need exists for a reference copy of a particular master, one can withdraw this master from the drawer for contact printing, and then return the master to the file.
The film strips inserted in the channels of the jacket act to somewhat thicken and thereby rigidify the jacket structure. In practice, the thickness of the microfilm strip is slightly greater than that of the empty channel defined by the ribs, so that it is snugly recessed therein. As a consequence, a loaded channel is somewhat thicker and stiffer than an unloaded channel. If all channels are more or less loaded, save for the lowermost channel, when a stack of jackets is stored in a file drawer or cabinet, a jacket having an unloaded and unstiffened lowermost channel which rests on the bottom of the drawer may buckle or slide under. As a consequence, the jacket will curl within the drawer and become inaccessible to the user of the file.
In a copending application Ser. No. 651,715, filed Sept. 18, 1984, entitled "Multi-Channel Transparent Jacket for Microfilm Strips," there is disclosed a multichannel transparent jacket whose channels are loadable with microfilm strips to create a microfiche master, the lowermost channel being pre-loaded with a removable dummy strip which acts as a stiffener to prevent the master, when partially loaded with film strips, from buckling under in a file drawer. In manufacturing this jacket, streams of molten plastic emerging from an extruder along parallel paths are fed continuously between upper and lower webs of transparent panel material into combining rolls in which the streams are compression-bonded to the webs to create the ribs, the combined webs then being sectioned into individual jackets. Also fed continuously into the combining rolls between the two adjacent streams which form the ribs defining the lowermost channel of the jacket is a tape whose width and thickness corresponds to those of a microfilm strip for which the jacket is intended. In sectioning, this tape forms the dummy strip pre-loaded in the jacket.
As pointed out in the above-identified copending application, since the dummy strip runs the full length of the lowermost channel in the jacket, it blocks the entry slot thereto. This makes subsequent removal of the dummy strip difficult, for the operator has no access by way of the channel entry slot to the lowermost channel.
In order to provide a dummy strip having a length that falls short of the full length of the lowermost channel, the copending application discloses an alternative method in which intermittently fed into the combining rolls in sequence are pre-cut dummy strips of the required shorter length, so that the leading edge of the dummy strip is aligned with the entry slot. In this way, one can push the dummy strip out of the lowermost channel by using the means available for this purpose in a microfilm jacket loading machine of the type disclosed, for example, in the Dorman U.S. Pat. No. 3,872,645, in which, as the microfilm is being loaded in any channel through the entry slot for that channel, it acts to advance whatever strip already occupies that channel. Hence, when loading the lowermost channel with a microfilm strip, the advancing strip will at the same time push out the dummy strip.
The practical drawback to this alternative method is that it is no longer possible to feed a continuous dummy strip tape into the combining rolls, and the need to dispense individual dummy strips is difficult to carry out in practice, for it requires a relatively complex strip dispenser mechanism for this purpose.